Shark migration shifts as ocean’s water warms up. Is that bad for Spring Break?

Just in time for Spring Break, researchers have released data showing the annual migration of blacktip sharks from Florida back north to North Carolina has changed in a way that’s not good for swimmers and surfers.

Data suggests only about one third of the number of blacktip are making the trip back up the East Coast from Florida, and it’s believed that’s because more sharks chose to stay off the Carolinas during the winter.

Never miss a local story.

Their annual trek to southern Florida has long been considered the largest migration in U.S. coastal waters, experts say.

For eight consecutive years, Stephen Kajiura, Ph.D., a marine biologist and shark researcher at Florida Atlantic University, has been observing the blacktip migration and he has documented as many as 15,000 sharks on any given day, reports the university.

“Last year, we saw a dramatic decline in the number of blacktip sharks that migrated south,” said Kajiura in a statement. “In fact, it was so low that we estimated the population to be about one-third of what we have seen in previous years. We want to make sure that these snowbirds come back to South Florida, because if they don’t, it will have a huge ecological impact in this region.”

Migrating sharks are a key part of Florida’s coastal ecosystem, because they weed out weak and sick fish. That’s beneficial to the region’s coral reefs and sea grass.

The result of the change in migration means swimmers and surfers might see more of these sharks along the northeastern coast year round.

Blacktip sharks are among the larger sharks in the sounds off N.C., reaching lengths of 8 feet, although most measure 6 feet or less, reports N.C. State. They have traditionally been a part of N.C. coastal sea life from late spring to late fall, and they usually moved into the sounds during the summer and autumn. They are fast predators, known to chase schools of menhaden and mullet, and will sometimes make spinning leaps out of the water while feeding, NC State reports.

Blacktip have been known to bite swimmers and surfers after mistaking their legs and feet for food.

Water temperatures determine where blacktip sharks wind up, Kajiura said in a statement. They leave the north when water temperatures drop below 71 degrees Fahrenheit and start heading south. They swim as far south as southern Broward County or northern Dade County.

Kajiura told National Geographic he believes this migrant shark population will permanently shift northward over time in response to long-term rising ocean temperatures. Many of these changes are already underway, experts say, impacting North Carolina’s commercial fishing industry, reported National Geographic.

Helping to back up Kajiura’s theories are marine biologists like Vince Saba, with the National Oceanic and Atmospheric Administration’s Northeast Fisheries Science Center. He told National Geographic that the waters off the northeastern U.S. have warmed faster than more than 99 percent of the world’s oceans in the past decade.

“We're not sure what the cascading effects might be,” he told TV station WPLG. “Someone still needs to look at that, but it is troubling that there used to be so many sharks, and now there are so few.”

The Florida Museum of Natural History recently released 2017 the data that showed shark attacks in US waters led the world, and most of them happened in two states: Florida and South Carolina.

There were 31 attacks in Florida and 10 in South Carolina. That’s double the number of unprovoked attacks South Carolina experienced the previous year, according to the survey.

North Carolina had one unprovoked shark attack last year, the data showed.